Electric zinc-distilling furnace and condenser.



J. THOMSON.

ELECTRIC ZINC DISTILLING FURNACE AND CONDENSER. APPLICATION FILED 1AN.19,1916.

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J. THOMSON.

ELECTRIC ZINC DISTILLING FURNACE AND CONDENSER. APPLICATION FILED IAN. I9, 191e.

1,265,973. Patented May 14, 1918.

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HAS' ATTO /EYS I. THOMSON. ELECTRIC ZINC DISULLING FURNACE AND CONDENSER.

APPLICATION FILED JAN. I9, 1916. V Y 1,265,973. mame@ may 14, M8.

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JOHN THOMSON, OF N EW YORK, N. Y., ASSGNOR TO JOHN THOMSGN PRESS COMPANY, 0F JERSEY CITY, NEWA JERSEY, A CGBPORATION 0F NEW JERSEY.

ELECTRIC ZINC-DISTILLING FURNACE AND CONDENSER.

Specication of Letters Patent.

-latented May 14, 1918.

Application led .anuary 19, 1916. Serial No. 72,906.

To aZZ whom 'it may concern.

Be it known that l, JOHN THOMSON, a citizen of the United States, and a resident of the borough of Manhattan, city of New York, county and State of New York, have invented vcertain new and useful improvements in Electric Zinc-Distilling Furnaces and Condensers, of which the following is a speciicatibn, reference being made to the accompanying drawings, forming a part thereof.

This invention relates to the metallurgy of zinc having particular reference to the purification of impure spelter by the distillation and condensation thereof in an electric furnace, and the objects are to increase the rapidity and effectiveness, and decrease the cost, of such operations.

In the accompanying drawings which form a part of this specification there is represented a preferred Inode of realizing the ends in view but the invention is not necessarily confined to the precise details shown in the drawings and described herein. ln the said drawings Figure l is a vertical, transverse center section of the furnace and its condenser, taken as on the planes indi- A of F ig. 2 and lines A and A1 of Fig. 3; Fig. 2 is a vertical longitudinal center section of the furnace, taken as on the planes indicated by line B of Figs. 1 and 3; Fig. 3 is a plan of the furnace and condenser, their covers being removed; this iigure is a view taken as on the plane E of Fig. l; Fig. 4l is a transverse section of the condenser, taken as on the planes indicated by lines C of Figs. l and 3; Fig. 5 is a de.

tached, enlarged longitudinal section of a trapped tap for permitting the continuous flow of condensed metal and Fig. is a transverse section of said tap, and is a view taken as on the plane indicated by line l).A

The heating system. of the furnace is comprised in a carbon resistor, F, formed of two slotted plates, 7, 8, producing a 21g-zag elec- `tric circuit, attached-by a connector, 9, to

operate in series by electriication from right and left hand terminals l0, il.

Beneath `the resistor is a shallow trough or open tank, l2, which contains thel bath of molten spelter, i3, supplied by a spout, 14, preferably located in ,nace opposite from that in which the termi- `of the furnace.

the end of the furnais are set. Av novel feature in this trough is that its end, under thev spout, is depressed to form a sump, l5. The major portion of the bottom of the trough is provided with a rather sharp slope, i6, declined toward the sump, and it is designed to receive a shallow charge of fluid metal. A large emergency opening, l?, in the end-wall of the trough, is in'closed by a removable refractory, 1.8, having therein a small tap-hole, 19,

Y. located near to the bottom of the sump.

@ne object of this construction is to permit lead or any metal of greater density and having a higher furning temperature than zinc to precipitate and flow to and accumulate in the sump, from which, at intervals, it is drawn olf through the tap hole, 19. Also, another object of the invention is to provide a construction whereby, when charging metal is delivered through the spout, plunging directly into the sump, the whole of the zinc in the trough will not be materially agitated. A prime advantage of the foregoing conditions is that little if any lead will be fumed irrespective of the length of time the furnace may be run. Moreover, as the quantity of metal contained in the shallow portion of the trough is relatively normal, it may at times be completely eX- hausted, in the form of fume, down to or .even below the sump-level, as 20, when the latter can .be entirely withdrawn. This is of particularA advantage when changing from one class of spelter to another, as the residual loss is thereby minimized.

As the rising velocity of the fume from the bath toward the resistor is comparatively slow it becomes more or less super-heated. ln order to eliminate some portion of this super-heat and yet to prevent a free upward escape of heat from the rresistor itself, an overlying compound septum is provided formed by a lower series of refractory plates, Q1, spaced to produce a plurality of central slits, 22, and above these plates is another series, 23, set closely together but leaving openings, 24, 2li-2, at the end walls ln this wise, there is formed a primary or resistor chamber, H, an intermediary septumchamber, l, and an or fume chamber J, from whence centrally located port, leads to the conment is that the fume passes up through the slots of the lower septum, deflects right and left, and flows horizontally through the septum chamber, as arrows a, rises throughvthe end openings of the upper septum, as arrows b, flowing along the end walls of the furnace and thence along its side walls and the upper l surface of the upper septum and also the roof, iinally'reaching the port, as arrows c.

trolled at the roof by employing a primary -layer of carbon slabs, 26, having freely l condenser.

set thereona layer or layers of heat in` sulating bricks, 27, whichy may` be removed or added to permitting a more or less free radiation` of heat; which will be largely that contained in and given up by the fume. Thus, while the temperature of the fume when in the resistor chamber may besay, 1,350", C., it is feasible to diminish it by some 200 or 300, which would be` about as low as would. be desirable for condensation to liquid metal, at its entry to the Obviously, in such circumstances, the capacity of a condenser of any given dimensions would be substantially en 'hanced. Or, stated conversely, the temperature of the resistor may be carriedv higher, with thermal advantage, than would otherl wise be permissible.

In the first blowing-in of a zinc distilling furnace, considerable losses are incurred through absorption of zinc in the brick-work,J particularly by porous heatA insulating bricks. This objection can be largely minimized by incasing the ends, sides and bottom of the refractory bricks, 28,

which form the general furnace chamber with thin strips of metal or asbestos-board, as 29. By simply observing that this bar rier-casing, which can be made with few or.

even no joints, is suiiciently protected as not to fuse or Ibe decomposed, a complete seal is interposed between the inner courses of dense refractory bricks and outer courses of porous heat insulating bricks andthe primary loss of zinc and time becomes nominal.

The coordinating condensing feature of the invention will now be described. With the complete temperature control and the high thermal efficiency obtainable in an electric furnace of the type herein denoted, it is feasible to precipitate, in the sump, nearly all of the lead and` iron usually contained in low gradelspelter; but with respect to cad-v mium, which is frequently present in spelter, such a precipitation either does not occur, or at the best to a` very limited extent. The

reason for this is that the' normal boiling point of cadmium may be taken to be 780 C., as compared930 foi` zinc. general terms, cadmium'will'both boil and beginto condense at a temperature of 150 C., less than zinc. In practice, the fume of gether; and so, too, they may condensetogether, that `is when the condensing temperature of the cadmium will have been reached. The foregoing also applies to other metals; as, for example mercury. Ad-

-vantage is taken ofvthese physical properto the furnace port which receives the outowing fume at some temperature sensiblyhigher than the condensing point 0f zinc. Within the condenser are a series of staggered baffle-plates, 303,-' shorter than the width of the casing, thereby forming endspaces, the fume flowing in a sinuous, horizontal plane along and between the plates andaround their ends, as shown by arrows i. The condensed metal is collected'in the bottom of the casing, forming a bath as 31, in which the lower portions of the baiiie plates are immersed,land this bath is maintained ata constant depth by means to be later described. Toward the outer Vend of the condenser two plates are shown, 32, 32a,

- which are the full width of the casing except where upper portions of ,the ends are'cut away to form spaces, as 33, 34. Thus, all of the metal to the right hand side of plate 32 is segregated in a common bath; but any metal condensed in the space R, or in the space S, between the rear plates, is separately contained therein and is not in communication with the larger forward section. In other words, both fume and metal iiow around the ends of the forward plates, while at the rear plates the fume only is free to flow, the liquid metal being confined. Now, by a proper control of the temperature of the condenser, as by its rate of heat radiation 'to atmosphere, whereby the f all of the temperature from the throat to the rear will be in a progressive ratio, as by the employ# ment of graduated insulation, indicated in dotted lines, z, Fig. l, all or a major portion of the zinc-fumecan be condensed when the zone indicated by the line C will have been reached and whereat the temperature will perhaps be about 750 to 800 C. 'In these circumstances, the cadmium will still be a vapor, continuing however to flow along as'indicated by arrows/w, and the temperature progressively falling to, say, 500 to `450, the cadmium will then condense and be Hence, in

both metals may rise and commingle tof y y Masacre entrained in one or the other or both of the rear spaces, R, S.l The foregoing description of fractional condensation contemplates an operation under ideal conditions. ln practice, ,owing to pulsations in the flow oi fume, atmospheric conditions affecting the rate of heat radiation, etc., the'zone of demarcation will fluctuate correspondingly, whereby a certain proportion of cadmium may be condensed with the zinc in the main forward compartment, or zinc may be condensed ewith the cadmium in one or both of the rear compartments. For usual commercial purposes, however, even such a result is satisfactory, for the reason that the objectionable quantity of cadmium in spelter does not exceed, ordinarily, from to ,5U of one per cent. and an elimination oil the major portion thereof is adequate.

To obtain the very best results in condensation such as a high rate of precipitation, uniform temperature and with a minimum of attention on the part of the operatorgthe reserve hath or baths, should be maintained at a constant depth; which means that the zinc should low out as rapidly as it is condensed. To accomplish this, the essential conditions involved are that the means ein# ployed must be entirely7 automatic; that absolutely no air shall be permitted to enter; that the dow shall be free and ample and that there shall bel no possibility o freezing These conditions have been fully met and the desired end realized by the simple device shown in the drawings, particularly Figs. 5 and 6, consisting of a cylindrical plug, 40, havingan axial bore, 4l, butwith a dead end, 41a. Near to the dead-end is a vertical transverse opening, 42, passing through the cylinder and connecting with the horizontal axial'bore. This plug is inserted in a wall of the condenser, so that ther vertical opening shall face downwardly; the location being such that the inner intersection or the said vertical opening with the horizontal axial bore shall be the height, or depth, at which the bath, as 43, yisto be maintained. Whenever the level of the bath rises above the aforesaid plane, the ,liquid zinc immediately runs out. If the fixed plane is again reached, the low of zinc ceases, but as the vertical. opening is lled, no air can enter the condensing chamber. Moreover, as the lower surface of the plug is immersed in the bath the metal in the vertical openin cannot freeze or become in the slightest degree sluggish. To facilitate a rapid flow, the axial bore is shown tapered; but the same enect can be .obtained by setting the plug at a slope.

As shown in Figs. l and 3, the condenser is provided with three of these taps, that on the right hand side serving to automatically and continuously draw off zinc while two others, being in compartments R and S,

oi' reserve metal; the rate of dow alom surface of Athe bath toward tap ceedingly slow.; hence, in an opera long duration, there is an ideal oppo for an accumulation along the bottom condenser, ley-density displament, heavier metals, as cadmium out oi a lead out of zinc, or cadmium-lead out 35 zinc, limited oi course, by extent to which one or these metals may be diss in another. ln any event, by mai -f a dead bath the lopportunity for pre" tation or metals having a greater den than zinc is compounded; rstlygto a extent, in the trough-sump and, secon i a minor extent, in the condenser itself.

`What l' claim is:

l. An electric furnace for distilline spels ter having a condenser in which therE a plurality of staggered plates around ne ends of a portion of which both :lume and condensed metal may flow but around other portion or" which only fume can il 2. An electric furnace for distil'ing ter having a condenser connected the which condenser has a plurality of maggered plates between and around the ends which condensed metal is contained as main or common bath, and another velate or plates around the end or ends of v.;7 h fume may dow but whereby metal condense-d thereat is separated from the main bate.

y 3. An electric furnace for distilling sp'fter contaminated with metal 6l greater density than zinc, which furnace has an attached condenser that is provided n means for constantly withdrawing metal, as and when condensed, from the upper tion of a bath, or baths, contained w the said condenser.

ln an electric 'urnace for distl ng spelter contaminated with another metal, or metals, .fi-condenser having a plurality ci" automatic trapped taps for withdrawing' the condensed metal from different vertical zones ol said condenser.

5. in electric -furnace for distilling spelter having a condenser attached thereto w ich condenser is provided with a trappe 'ap in which the sealing end is immerse in a bath contained within said condenser.

6. A liquid metal condenser having a trappe 1 tap rorrncd by alplug having a nerizontal axial bore terminatingat a dead-end portion, but near to the surface, of a bath and a vertical connecting opening, the latter contained within the condenser. 10 being setto face downwardlyand be `i'm- This specification "signed andy witnessed mersed beneath the surface of a bath conthis 18th day of January, A. D. 1916.

5 tained within the condenser. K Y JOHN THOMSON.

7. A liquid metal condenser having a. Signed in the presence oftubular trapped tap for withdrawing metal RALPH M. THOMSON, as and when condensed from any desired J. R. AGNEW. 

